First, my thanks to you and the other responders to the post. The replies
have certainly been interesting, as well as somewhat varied.
I have a comment and a question for you. First, the comment regards use of
the term "insulation", as you note in your reply remarks. That word did
raise some questions in my mind when I first read the article. My
conclusion then, and now, is that the author chose that word poorly. I
think a better word would have been "isolation", since I think the idea was
to isolate motor drive currents (both "hot" and "return") from the
vehicle's chassis. While it certainly does mean that the motor is
insulated from the chassis, the key element (from an RFI perspective) is
that the motor be isolated from the chassis. Does that help?
Now, the question: I do not own a Prius Hybrid or any other brand or model
of hybrid or all-electric drive vehicle. What I am not certain about is
whether the gas engine in the Prius runs at all times, or are there
instances in which the car is all-electric? My thinking (could be wrong)
is that there might be differing levels of RFI present in these vehicles,
depending upon whether the gas engine was operating or not. Your comments
about the battery in the Prius are quite a surprise to me, as I had
imagined some fairly hefty batteries electrically stacked in series to do
the main job of moving the car.
No matter what, it is good to know that at least in some cases, operation
of HF mobile radios is possible in these cars. Thanks.
> [Original Message]
> From: Roger (K8RI) <firstname.lastname@example.org>
> To: <email@example.com>
> Date: 4/10/2012 7:52:18
> Subject: Re: [RFI] RFI issues in electric (or hybrid) vehicles
> On 4/10/2012 6:40 PM, Dale Svetanoff wrote:
> > List mates:
> > The link below leads you to an article from Electronic Design magazine.
It concerns RFI issues in electric drive vehicles (and, by extension,
hybrids, as well). The primary focus is on the interference caused to the
entertainment system ("broadcast") radios within the vehicles. My personal
view is that the situation is almost surely applicable to communications
radios, as well, especially those used for HF communications.
> > Here is the link:
> We have a Prius Hybrid: No RFI issues to either the entertainment center
> or the rig.
> Most of the Hybrids I've seen/driven had too small a battery and light
> gauge wiring to run much of a radio. The battery is so small the
> manufacturer recommends you do not wire directly to the battery, but
> either through the switch, or a relay that is energized only when the
> ignition is on. Two other hams have newer models and they do not have
> any RFI issues either. I'd suggest a heavy duty battery placed in back
> along with a much larger alternator to keep it charged.
> The first sentence is a blanket statement that is not true: "To enable
> radio reception in electric vehicles, manufacturers must install filters
> and insulate cables, since electrical signals will otherwise interfere
> with music and speech transmissions" as I can point to 3 examples from
> different years that have no problems in either the car entertainment
> system, or the ham rigs. I can understand filters when necessary and
> shielding, but "Insulation"?
> Therefor this appears as an article that was not well thought out or
> > (Note: Due to length of the link, I hope it all comes thru the
reflector intact. I am in hopes that you will be able to click anywhere on
the link and succeed in getting to the article.)
> It works fine in Thunderbird.
> > To be honest, I was disappointed in the article's lack of substantial
technical detail. (Although Electronic Design is not a publication devoted
specifically to EMC/EMI issues, it is targeted to the electronic
engineering community. Therefore, I was a bit surprised that this article
is pretty much at the lay person level. Nevertheless, I felt that some of
the comments might be of interest to readers on this reflector.)
> The first sentence being a blanket statement that is not true hurt the
> credibility of the article and author.
> > One aspect of the automotive RFI issue did catch my interest: A primary
dictum in RFI control is that you do all that you can to contain an RFI
source (in this case, the power converter) so as to minimize propagation of
interference via direct radiation or via the associated wires and cables.
("Containment" also means that I/O lines should be well-filtered.) Note
that nowhere in the article is containment of the source mentioned.
Instead, a lot of effort has been placed on routing of wires and insulation
of the high power drive motor from the chassis of the vehicle. (These
motors are typically electronically commutated DC types, no brushes.) One
must guess that size, weight, and cost probably factor into the decisions
to work placement and isolation issues, rather than containment.
> > I, for one, would be delighted if someone in the automotive industry
would reply to this posting with some supporting information as to what is
being done in today's electric and hybrid drive vehicles for RFI control,
especially as regards communications (be it for broadcast or two-way
applications). I would also welcome comments from anyone associated with
the Fraunhofer Institute and the work described in the article.
> > Finally, I am wondering if any list members have installed either a ham
rig (HF and/or VHF/UHF) or a scanner in an electric drive nor hybrid
vehicle, and if so, were there any significant RFI issues to contend with?
Please post so that we can all share in your experiences. Thanks.
> As I said above, I know of three hams who drive a Prius (all different
> years). Ours is one of the oldest ones, while a friend drives on about a
> year old. No RFI issues at all.
> Roger (K8RI)
> > 73, Dale
> > WA9ENA
> > Sr. EMC Engineer
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